Perfectly safe if the kite is the right size and you've secured the spike correctly. Also it will give you a chance to make sure the lines are correctly attached before you hook in which is the most dangerous part of self launching.

I use a karabiner for self launching & landing. But those screw in the ground spike things are no good for sandy beaches IMHO. They might be ok for 'solid ground' ie. mud, but sand is too soft to give a good strong fixing point. I've tried one before and it came out of the sand, thankfully we were close enough to catch the kite before it sped away with a bar & lines with a sharp spike attached adding to potential damage of others \ property.DO NOT BUY ONE

Like James says, it lets you double check the lines are correct, just like if someone was launching you.It is also imperative, to have the correct sized kite up for the conditions at the time if you are going to go for this method, or you could potentially have a world of woe

When I first started launching like this I was using a cheap rubbish karabiner, one day it snapped, I had a bit of a run after my kite, thankfully no-one was around to see it or get involved. I was very lucky. So buy a karabiner from a climbing shop, with a high breaking point

I've found the best way is to have some depower pulled in and walk the kite around to where it is pretty steady, it will bounce around a little. But as long as you are quick, but not rushing, everything works very, very well for launching & landing

Some people used to use the old Ikea bags filled with sand. I've seen some use their kite bags filled with the pebbles from the beach. I guess you could use your kite bag filled with sand.

A high breaking point karabiner is essential but I used a stake on Friday in the soft sand at Aberavon, it was more than good enough for the job.

The problem with using anything like a kite or ikea bag is that the stitching will be a massive weak point as they're not designed to be used in this way.

Basically if you're using either a stake/sand bags/ikea bags use some common sense, depower the kite, don't walk away from the kite if you can feel the anchor moving, don't use this method in super gusty winds and pick the correct sized kite.